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Discussion Starter #1
Hi guys!

My battery has died twice recently after not using it for 2 days in a row. I think it is extremely likely that this is due to HFL card defect. So question is what is the quickest and easiest way to make sure HFL is indeed the culprit beyond doubt.

There must be a fuse somewhere so that once I pull that fuse, the parasitic draw will stop. So which fuse is it? Any ideas?

I am going to study the past threads right now, but it would be great if some guys can give me a quick head-up so that I can jump start and send my wife on her way with confidence.

TIA
 

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Discussion Starter #2
Quick update:

I removed the negative terminal of battery, and tested the current. The reading is about 3A. So there definitely is a parasitic draw. Then I removed fuse #5 and the draw went to basically 0. Great. So I removed the bluetooth card and re-connected the two plugs near it. Then I read it again. The reading is about 0.48A. Not zero! Does this look normal? If not, apparently there is something else going on. Anybody knows what else is connected to fuse #5 and can normally lead to a draw of 480mA? Any advice is much appreciated.
 

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FYI: The quickest way to know if the HFL is bad is by clicking the HFL Button on the Steering Wheel..
It might do the classic "Beep Beep" but the automated voice wont come on or respond to your inputs.
or Clicking the HFL button will do nothing.

Those 2 are the quickest way to know if the HFL is Bad.
 

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Also there is never going to be ZERO Draw..
The AFAIK it must be between 0.250-0.350A since the ECU and other stuff requires electricity to Save settings and such. Any draw above 0.5A is parasitic.. 3A is overkill...
 

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Discussion Starter #5
Can anybody remember the current draw of a healthy MDX? 480mA seems a bit high. Don't know what else is wrong with fuse #5. Thanks.
 

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Discussion Starter #6
If I disconnect fuse #5, it is 0.02A, which is 20mA. This fact has been verified by many source online. So something else on fuse #5 has to explain the majority of the 460-480mA draw.


Also there is never going to be ZERO Draw..
The AFAIK it must be between 0.250-0.350A since the ECU and other stuff requires electricity to Save settings and such. Any draw above 0.5A is parasitic.. 3A is overkill...
 

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Discussion Starter #7
It is all good man! Turns out it is how you measure the current. With fuse #5 removed, the amperage reading will drop to 20mA in a second. However, with fuse #5 in, and HLF card out, it would take longer. The amperage reading will first drop to 460mA and stay there for quite a while, then it WILL DROP to 20AM and STAY THERE. With fuse #5 in and HLF card connected, the reading will drop pretty quickly to about 240mA and stay there for a while, then it will surge up to 2.8A and then drop back to 200mA, then to 240mA and repeat. Now I have complete confidence that HFL is the culprit! I won't even bother to bake it since I do not use it much anyway. Cheers!!!

BTW, this video is helpful.


Anybody knows which relay is the AC relay he talks about and where can we buy an updated version of the AC relay? I am scared to xxxx today and I'd rather replace that ****ty AC relay sooner than later. It is never fun to get stranded on the road! Cheers man, let's all get them replace now!
 

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Today I join you. My new to me mdx had a drained battery this morning. 2008 no tech/nav. My wife had to jump start to get home from work. I pulled the negative and put my meter inline. I heard a relay click. It reads 2.4amps. That's too much me thinks. Well I reconnect it and learn the hard way about the radio security but I got the code online. I research here and find out about the ac relay and hfl unit. My hands free isn't working so that must be it! Well I take the console cover off and it was already disconnected! I connected it and still nothing. So I baked it and it's fixed. I check my amp draw again this time with my dc clamp to avoid disconnecting the battery. 3amps. After a few minutes it goes down to under 1 amp? Oh well. BTW, I pulled the ac relay and that made no difference. Besides, my ac clutch turns on and off just fine. If the battery keeps going dead I will get it tested. Any other ideas?

The ac relay is in the secondary fuse box. The engine bay, opposite the battery, second from the left as you look at it. Mine was next to a blue relay. It is black.
 

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Discussion Starter #9
It is actually quite simple. You need to make sure that all doors are closed when you do the test. Also when it dropped to 1A, do not give up. Keep waiting. It will then drop to 20mA. I took me quite a while to figure this out.

Today I join you. My new to me mdx had a drained battery this morning. 2008 no tech/nav. My wife had to jump start to get home from work. I pulled the negative and put my meter inline. I heard a relay click. It reads 2.4amps. That's too much me thinks. Well I reconnect it and learn the hard way about the radio security but I got the code online. I research here and find out about the ac relay and hfl unit. My hands free isn't working so that must be it! Well I take the console cover off and it was already disconnected! I connected it and still nothing. So I baked it and it's fixed. I check my amp draw again this time with my dc clamp to avoid disconnecting the battery. 3amps. After a few minutes it goes down to under 1 amp? Oh well. BTW, I pulled the ac relay and that made no difference. Besides, my ac clutch turns on and off just fine. If the battery keeps going dead I will get it tested. Any other ideas?

The ac relay is in the secondary fuse box. The engine bay, opposite the battery, second from the left as you look at it. Mine was next to a blue relay. It is black.
 

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Discussion Starter #10
I found out from the video that the upgrade part number is
39794-SDA-A05

This thing is about $15 on Amazon and ebay. Weird that it is said on Amazon that it won't work with 2007 MDX. Anyway, lots of people say that $5 part from Autozone would work just fine. Just want to know if anybody can vouch for Autozone generic part's quality? Is it just as good as Honda branded part? Are Honda parts just rebranded common generic part? If I go to Autozone, what should I tell them to pick the right relay? Thanks.
 

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Most Honda stuff is made by DENSO in the case of the relay is made by OMRON which is a giant OEM Supplier...
Autozone does not sell branded relays, pure generic china.. I would got with the Upgraded OEM Part since you don`t want to mess with the electrical stuff with cheapo parts just to save 10 bucks.
 

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Discussion Starter #12
I took a look inside the relay box. There are 6-7 identical relays. If the AC relay tends to go bad, how about the rest? If we replace all of them at $20 each (after tax), that is not very cheap.

The Mexico-made HFL is defective, and the USA-made Omron relay is defective. How bad could China-made relay be? These things are not rocket science. I bet the cost is less than $1 each. Feels pretty silly to pay $20 for it.

P.S. Found this information from Amazon. The updated Honda parts is made in Vietnam by Mitsuba. Yeah right, just like Johnson Control made in Mexico.

Both relays have the same terminal configuration and either plug in in the necessary location. However, I cannot with 100% confidence tell you that these two relays are interchangeable. There could be a difference in ratings. The 39794-SDA-A03 is made in the USA by Omron. The 39794-SDA-A05 is made in Vietnam by Mitsuba. The 39794-SDA-A03 shows to fit the 2009 year as where the 39794-SDA-A05 does not
 

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It all depends on the Amperage.. Perhaps the A/C one has more load due to the A/C Clutch while the others are below the spec or simply not being taxed at all. The new "Improved Unit" might have better quality control to withstand the needed load.
 

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Discussion Starter #15
It makes sense. w/ fuse 5 and no HFL control unit, it is 0.02A for me. With control unit, it cycles through 0.2x to 3.xA. So the addition of HFL could raise the normal draw to 0.2xA. If parking for several weeks in a row, it makes sense to disconnect HFL then.
 

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Just disconnect the HFL module and see if the issue goes away. I would bet you some $ that is your problem. Very common problem. Acura was pretty crappy not to issue a recall on these faulty HFL modules
 
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